He was the son of Alfred Leune (2 September 1857, Rouen, Normandy – 9 December 1930, Paris) and Céline Blanche "Léonie" Daix (1871–1942).
[8] The Leunes accompanied the Greek Army in the field in different campaigns, and their many articles and photographs provide a vivid testament to the valor, horrors and hardship of that war from the perspective of both combatants and civilians.
In 1913, Jean and Hélène both contributed chapters to the book Dans les Balkans, 1912–1913 : récits et visions de guerre, that describe their wartime expériences.
After spending the first part of the campaign in France, he was sent to the Corps expéditionnaire d'Orient, where he flew reconnaissance missions and organized a battalion of Greek volunteers in Moudros.
Hélène Leune, who had been serving as a Red Cross nurse, died in Vitry-le-François (Marne), France during the bombardment that took place in that town on 18 May 1940.
[14] Jean Leune was a remarkable observer and he performed a series of aerial reconnaissance missions with the Corps expéditionnaire d'Orient that yielded valuable information every time.
[10] As part of a military aerial competition, in August–September 1919, Captain Leune flew from Paris-Marseille-Pisa-Rome-Vallona-Thessaloniki-Constantinople, covering 5,500 km in 50 hours of flight time.
He made the voyage with a mechanic, Perrin, and a radio operator, Dugré, aboard the Chimère, a Farman F.50 twin-engine bomber (275 h.p.
[21] Jean wrote three novels during the 1920s: L'Éternel Ulysse, ou la Vie aventureuse d'un Grec d'aujourd'hui, a satirical depiction of contemporary Greek society (1923); Le Malfaisant, an allegorical story about good and evil set during World War I (1927); and Au temps des Vikings : Nora la blonde, vierge, au bouclier, a historical adventure set in Scandinavia around 1000 A.D. (1928).
On 29 January 1930, the couple flew on the maiden flight of the airborne postal service from Alger to El Goléa, established by the Compagnie aéropostale.
In response to the German invasion of Poland, France declared war on Germany on 3 September 1939, and Leune was mobilised as a Reserve Officer that same month.